BBC News

Saturday, December 14, 2002

Genes may hold the key to anxiety

The discovery of a gene in mice that plays a role in learning to be afraid could provide clues to the origins of severe mental illness, say researchers.
Scientists at the Howard Hughes Medical Institute believe they have found one of the key elements in the process of "learned fear".

This is where animals, including humans, learn over time that something is a threat or danger, as opposed to the instinctive fear which animals are born with.

In studies of fear learning we could well have a excellent beginning for animal models of a severe mental illness

Professor Eric Kandel, Howard Hughes Medical Institute
The US team bred two groups of mice - one normal, and one lacking a gene called GRP - which earlier studies suggested might be linked to a particular region of the brain called the amygdala, which is often associated with fear.

GRP appears to inhibit the action of "circuitry" in the brain which learns fear.

The mice were "taught" fear by linking a specific noise with an electric shock.

Then their response to the tone on its own was measured.

Long freeze

Those with the GRP gene lacking had a greatly-enhanced fear response, "freezing" for much longer than the normal mice.

They were no more sensitive to pain, or increased instinctive fear.

Professor Eric Kandel, a member of the research team, said: "These findings reveal a biological basis for what had only been previously inferred from psychological studies - that instinctive fear, chronic anxiety, is different from acquired fear."

Anxious for drugs

In theory, the finding could start to shed light on the origins of anxiety disorders, and perhaps potential ways to treat them.

Professor Kandel said: "Since GRP acts to dampen fear, it might be possible in principle to develop drugs that activate the peptide, representing a completely new approach to treating anxiety.

"And while I don't want to overstate the case, in studies of fear learning we could well have a excellent beginning for animal models of a severe mental illness.

"We already knew quite a lot about the neural pathways in the brain that are involved in fear learning.

"And now we have a way to understand the genetic and biochemical mechanisms underlying those pathways."